A folding method to design linear retro-directive antenna array using hybrid circuits

In this paper, a novel folding method to design 90deg hybrids circuits for linear retro-directive arrays with arbitrary number of elements is proposed. Three-element, four-element, and six-element passive retro-directive array with experimental results are presented. The measured patterns demonstrate that the main beam is aligned with the incident angle. This approach can be implemented as an arbitrary odd-number and even-number linear retro-directive antenna array.